Process for the production of medium-to low-carbon ferromanganese alloys



United States Patent 3,551,141 PROCESS FOR THE PRODUCTION OF MEDIUM- TO LOW-CARBON FERROMANGANESE ALLOYS Minoru Matsuura, Kochi-shi, Japan, assignor t0 Kobe Steel, Ltd., Fukiai-ku, Kobe, Japan, a corporation of Japan N0 Drawing. Filed Aug. 25, 1967, Ser. No. 663,335 Claims priority, application0lgapan, Sept. 1, 1966,

58 Int. Cl. C22b 1/60, 9/10, 47/00 U.S. CI. 75-80 4 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to an improved process for the production of mediumand low-carbon ferromanganese alloys.

In the production of mediumand low-carbon ferroalloys of metals, such as manganese, which are hard to be reduced and easy to be carbonized, there has generally been employed a process which comprises the steps of producing silicomanganese as an intermediate high-silicon alloy and thereafter desiliconizing said highsilicon alloy with an manganese ore and a flux, due to the fact that the reduction method using carbon cannot be employed directly. The second step in the process described above has commonly been carried out by charging the intermediate silicomanganese, obtained in the first step, in an electric furnace in a cold solid state, together with the manganese ore and the flux, and refining the same upon melting. The desiliconization reaction of the second step is represented by the reaction formula given below, from which it will be seen that the manganese ore is reduced with silicon present in the intermediate silicomanganese, and this reaction generates heat which is advantageously used in the refining process.

However, since the desiliconization in the conventional process described above resorts to interface reaction between the single layers of slag and metal, there has been the disadvantage that the reaction period becomes inevitably long, causing a major portion of the heat of reaction generated to be wastefully lost as being heat loss, as caused by cooling of the furnace body, and thus making it impossible to make effective use of the heat for the refining reaction.

Namely, according to the conventional process, although heat is generated by the desiliconization reaction, the heat is smaller in amount thanthe heat dispersed before the refining is accomplished, so that it is necessary to make up for the balance of heat with the heat generated by the electric furnace. In addition, in practicing the conventional process, the intermediate high-silicon alloy produced in the first step, which is molten, must be cooled to solid for carrying out the second step, thus causing the heat possessed by said molten high-silicon alloy to be lost wastefully.

The present invention has for its object the provision of an improved process for the production of mediumand low-carbon ferroallys of metals, such as manganese and chromium, which have a strong afiinity with carbon.

According to the process of this invention, it is pos sible (1) to utilize effectively the heat generated during the production step of an intermediate high-silicon alloy, (2) to carry out the reaction between an ore and the intermediate high-silicon alloy, that is a desiliconization reaction, in a liquid state in an efiicient manner with said ore melting quickly, therefore (3) to obtain highly effective utilization of the heat throughout the process, and consequently (4) to produce a desired mediumor low-carbon ferroalloy at low costs.

According to the present invention, there is provided a process for the production of mediumand low-carbon ferroalloys, which comprises pouring a molten intermediate high-silicon alloy produced in the first step into a vessel such as a ladle and mixing said molten intermediate highsilicon alloy with an Ore and a flux, which have previously been heated to a temperature of 700 C. or higher, with stirring, whereby said ore is molten to accomplish desiliconization of said intermediate high-silicon alloy quickly, by making use of the intense heat generated during the reaction.

The process of this invention is adapted for use in the production of ferroalloys and particularly mediumand low-carbon ferroalloys of such metals as manganese and chromium which have a strong afi'inity with carbon.

The intermediate high-silicon alloy to be used in the present invention may be the ordinary high-silicon alloy which contains manganese or chromium depending upon the kind of a ferroalloy desired to be obtained, i.e. ferromanganese or ferrochromium. Namely, alike the ordinary one, the intermediate high-silicon alloy to be used in the present invention contains from 14 to 40% silicon in the case of silicomanganese and 40% or more silicon in the case of silicochromium, and may be -produced by the common refining process. It should, however, be noted that, according to the process of this invention, the intermediate high-silicon alloy is used in a molten state, Without being cooled to solid, for the reduction of an ore successively after the refining of the same has been completed.

The ore and flux to be used are heated to a temperature of 700 'C. or higher prior to the reaction with the intermediate high-silicon alloy. Such preheating of the ore and flux may be effected in a suitable furnace, such as a rotary furnace or shaft furnace. Preheating of the ore and flux is necessary for carrying out the refining of the molten intermediate high-silicon alloy in an eflicient manner by the reaction therewith but also has the advantage of calcining the ore. Because, in the case, for example, of maganese ore, since the manganese oxides present therein are all converted into trimanganese tetraoxide (Mn O as a result of preheating, silicon in the high-silicon alloy can be used for the refining reaction effectively, without being consumed by oxidation.

The temperature to which the ore and the flux are preheated is selected within the range from 700 C. to the softening points of said ore and flux. A temperature below 700 C. is unsatisfactory because the refining reaction can hardly proceed smoothly due to heat unbalance, whereas a temperature higher than the softening points of the ore and flux renders the handling of said ore and flux difficult.

As an ore, a manganese ore or a chrominum ore is used depending upon the kind of a ferroalloy desired, whether ferromanganese or ferrochromium. The flux may be a lime, e.g. slaked lime, as usual. The proportion between the ore and the flux may be determined in accordance with the operational standards for the conventional process.

The reaction between the intermediate high-silicon alloy and the preheated ore is desiliconization reaction on the part of the former and reduction reaction on the part of the latter, and as a result a slag is formed which primarily consists of silicon oxide. In the present invention, this refining reaction is carried out in a vessel such as a ladle, while stirring the reactants. Such stirring is obviously effective in mixing the reactants thoroughly with each other and thereby enabling the reaction to be carried out smoothly. The preheated ore and flux are molten immediately upon contact with the molten intermediate high-silicon alloy and the so-called homogeneous reaction takes place among the reactants in a liquid state.

The refining reaction can be accomplished with a satisfactory result by stirring the reaction mixture either mechanically or electrically, but the object of the reaction can be attained more positively by employing the shaking ladle method to be described hereunder.

furnace; Then, 400'kgs. molte'n silicomanganese of the Namely, the molten highsilicon alloy contained in a vessel such as a ladle is imparted with an eccentric'al rotation reciprocally, whereby the ore and the flux are sucked into the interior of the molten alloy abruptly being mixed therewith intensely, and thus the contact reaction can be attained highly efficiently. As a result, the yield of the product ferroalloy with respect to the ore and flux added can be improved remarkably and the refining reaction can be accomplished quickly in a very short period of time. The shaking ladle method briefly explained above is described in detail in US. patent specification No. 3,251,681.

As will be understood from the foregoing descrip tion, according to the process of this invention, in which the molten high-silicon alloy produced in the first step is directly used, without being cooled to solid, for the production of an objective ferroalloy by quickly desiliconizing it with the preheated ore and flux with stirring, it is possible to effect the melting of the ore and refining of the high-silicon alloy, with the heat generated intensively during the reaction and there is strictly no need of supplying heat externally. Furthermore, since the molten high-silicon alloy, produced in the first step, can be used successively and the refining of the same can be accomplished in a simple manner and in a very short period of time, it is possible to enhance the productivity and to reduce the production cost remarkably.

For the purpose of reference, the shaking ladle disclosed in the aforemetioned US. patent specification No. 3,251,681, may be used for practicing the process of this invention.

In order that the present invention may be more clearly understood, the production of mediumand low-carbon ferromanganeses by the shaking ladle method will be illustrated hereinafter, together with the results thereof. The ladle used, which is constructed as shown in the accompanying drawing, had a capacity of 500 kgs. and was rotated reciprocally at 92 r.p.m., i.e. rotated in the normal direction for 8 seconds, held stationary for 2 seconds and rotated in an opposite direction for 8 seconds, with an eccentric radius of 45 mm. The compositions of the ores and fluxes used are shown in Table 1 below.

EXAMPLE 1 In the above-mentioned ladle, which had previously been heated to about 800 C. by an oil burner, with 30 composition shown in Table 2(1) was poured in the ladle at 1430 C. and the ladle was shaked continuously for 20 minutes. 570 kgs. product ferroalloy of the composition shown in Table 3.( 1) and 600 kgs. slag were obtained.

EXAMPLE 2 560 kgs. manganese ore and kgs. slaked lime were heated to about 700 C. in a coke-type shaft furnace and chargedin the ladle which was still at a high temperature immediately after completion of the process described in Example 1. Then, 400 kgs. molten silicomanganese of the composition shown in Table 2(2) was poured in the ladle at 1400 C. and the ladle was shaked for 24 minutes continuously. 450 kgs. product ferroalloy of the composition shown in Table 3 (2) and 690 kgs. slag were obtained.

' EXAMPLE 3 500 kgs. manganese ore and 210 kgs. slaked lime were heated to about 700 C. in a rotary furnace and charged in the ladle which was in a state as in the preceding example. Then, 400 kgs. molten silicomanganese of the composition shown in Table 2(3) was poured in the ladle at 1360 C. and the resultant mixture was shaked for 12 minutes continuously. 570 kgs. product ferroalloy of the composition shown in Table 3(3) and 490 kgs. slag were obtained.

TABLE 1 Manganese ore Slaked lime, Mn S102 Fe CaO P 0210 Composition, percent 52 0 5 4 0.07 98 TABLE 2 Composition of molten silicomanganese, percent I claim:

1. A process for the production of mediumto lowcarbon ferromanganese alloys, comprising preheating a charge consisting of manganese ore and a flux to a temperature ranging from 700 C. to below its melting point, admixing a molten manganese containing high-silicon alloy with said preheated ore and flux, and vigorously stirring the ingredients of the mixture to ensure a homogeneous reaction thereof.

2. A process according to claim 1, wherein said manganese ore and flux are preheated to a temperature such that the manganese oxides present in said ore are substantially all converted to trimanganese tetraoxide.

- 3. A'process according to claim 1, wherein said highsilicon alloy, containing from 14 to 40% silicon, and said preheated ore .and flux are admixed and stirred in a shaking ladle provided with an eccentric reciprocal rotation.

4. A process according to claim 3, wherein the mediumto. low-carbon 'ferromanganese alloys produced contain from about 75 to 80% Mn, from about 1.0 to 2.0% Si, from about 1.5 to 2.0 C and from about 0.08 to 0.15 P.

References Cited UNITED STATES PATENTS Udy 75-129X Bauer 75129X Dery 75--129X Kuhlmann 75133.5

L. DEWAYNE RUTLEDGE, Primary Examiner 5 JOSEPH E. LEGRU, Assistant Examiner US. Cl. X.R. 

